Author Topic: RPM signal  (Read 576 times)

Offline RyanC

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RPM signal
« on: October 16, 2016, 08:46:41 pm »
Right so I need to get the RPM signal for the coil. It says use the negative of the coil.
I don't know how it's confusing me but it's a 3pin plug you have a 12v feed to the coil (black wire), an ECU trigger wire (black and green wire) and a ground (brown wire).
If I went straight to the ground wire I can't see it getting an RPM signal. So I'm guessing I need to go onto the black and green wire that is the ECU signal wire so I grounds when the ECU tells it to so it will give you the RPM signal?
Can anyone point me the right way?

Thanks

Offline G40supercharged

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Re: RPM signal
« Reply #1 on: October 17, 2016, 08:12:27 am »
On an old style coil the contact breaker switches the current through the coil. The positive side of the coil permanently attaches to +12V (through the ignition switch) and the contact breaker provides the switching to ground on the negative side. This will give a ground to 12V RPM signal at the negative terminal. On a Polo the coil has some electronics attached to the back of it that does the switching rather than a contact breaker. The +12V and ground are permanent power connections. The third signal from the ECU is a trigger for the electronic switch that then fires the coil. This signal will give you the RPM.  The ECU signal will only provide a low current so be careful what you connect to it; for instance shorting it directly to ground may damage the ECU.   

Offline RyanC

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Re: RPM signal
« Reply #2 on: October 17, 2016, 06:03:06 pm »
It's a new style coil. I think I got the answer though there is a flap that covers the coils primary coil terminals. 15 and 1 I've been told if I connect it to 1 that will give me my square wave RPM signal